This invention is generally directed to toner dry and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing novel side chain polyester resins, and process for the preparation thereof. In embodiments, there are provided in accordance with the present invention toner compositions comprised of certain side chain polyester resin particles, and pigment particles comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, or brown components, or mixtures thereof thereby providing for the development and generation of black and/or colored images. In embodiments, there are provided in accordance with the present invention a process for the preparation of a side chain polyester by free radical polymerization of endene polyester resins. The toner compositions of the present invention in embodiments possess a number of advantages including low melting characteristics, broad fusing latitude, excellent blocking characteristics, excellent admix characteristics, are of low cost, and possess excellent nonvinyl-offset properties. The toner compositions of the present invention can in embodiments be generated by a process involving (a) the melt polycondensation of about 1 mole equivalent to about 2 mole equivalent of diols such as 1,2 -propanediol and diethylene glycol with about 0.9 mole equivalent to about 1 mole equivalent of diacid such as terephthalic acid or diester such as dimethyl terephthalate yielding a polyester oligomer with a low degree of polymerization, such as with a number average molecular weight (Mn) of from about 1,000 to about 10,000 grams per mole, and a weight average molecular weight of from about 2,500 to about 100,000 grams per mole as measured by gel permeation chromatography; (b) followed by the addition of a difunctional unsaturated monomer such as dialkyl maleate or maleic anhydride of from about 0.001 mole equivalent to about 0.1 mole equivalent, thereby enabling the capping or termination of the polyester oligomer, known as an "endene polyester" containing an unsaturated moiety predominantly at the terminal end(s) of the polyester oligomer as illustrated, for example, with reference to the following ##STR2## and (c) subsequently followed by the addition of a free radical polymerization initiator such as organic peroxides like benzoyl peroxide, lauryl peroxide or azoisobutyronitrile, and the like, and resulting in the polymerization of the oligomeric endene polyester to provide a side chain polyester resin as illustrated by the following formula ##STR3## wherein m, n and o represent the number of monomer segments present, R is independently selected from the group consisting of a hydrogen and alkyl, R' is independently selected from the group consisting of arylene and alkylene, R" is independently selected from the group consisting of an alkylene and an oxyalkylene; and with, for example, a number average molecular weight of from about 1,500 to about 50,000 grams per mole as measured by gel permeation chromatography, and a glass transition temperature of from about 40.degree. C. to about 70.degree. C., and more preferably of from about 50.degree. C. to about 64.degree. C. as measured by the Differential Scanning Calorimeter. In embodiments, the side chain polyesters of the present invention can be generated by a process comprising (a) the melt polycondensation of a diol such as 1,2-propanediol and diethylene glycol with a diacid such as terephthalic acid or a diester such as dimethyl-terephthalate and a difunctional unsaturated monomer such as dialkyl maleate yielding directly the endene polyester oligomer with a low degree of polymerization, such as with a number average molecular weight of from about 1,000 to about 6,000 grams per mole as measured by gel permeation chromatography; and (b) subsequently followed by the addition of a free radical polymerization initiator such as benzoyl peroxide and the like, thus resulting in the polymerization of the oligomeric endene polyester to provide a side chain polyester resin with a number average molecular weight of from about 1,500 to about 50,000 grams per mole as measured by gel permeation chromatography, and with a glass transition temperature of from about 40.degree. C. to about 70.degree. C., and more preferably of from about 50.degree. C. to about 64.degree. C. as measured by the Differential Scanning Calorimeter. Alkyl includes components with from 1 to about 25 carbon atoms like methyl, ethyl, propyl, butyl and the like; aryl includes groups with from 6 to about 24 carbon atoms like phenyl, benzyl, halogenated phenyl, and the like; alkylene includes groups with 1 to about 12 carbon atoms like ethylene, propylene, butylene and the like; and oxyalkylene includes groups with 1 to about 12 carbon atoms like oxypropylene, oxyethylene, oxybutylene and the like.
Examples of advantages of the toner composition of the present invention comprised of a side chain polyester include low fusing temperatures, such as from about 120.degree. C. to about 145.degree. C., and therefore, lower fusing energies are required for fixing thus enabling less power consumption during fusing, and permitting extended lifetimes for the fuser system selected. Furthermore, the toner composition of this invention possesses a broad fusing latitude, such as from about 40.degree. C. to about 100.degree. C., with minimal or avoidance of release oil, which inhibits the toner from offsetting onto the fuser rollers usually associated with ghosting or background images on subsequent copies. Furthermore, the fused image obtained from the toner composition of the present invention in embodiments does not substantially offset to vinyl covers, such as those utilized for binders.
In designing polyester resins for toner composition, it is generally required that the glass transition temperature of the resin be from about 50.degree. C. to about 65.degree. C., and preferably no less than about 55.degree. C. so that the toner particles do not aggregate, coalesce or block during manufacturing, transport or storage, or until the toner is required for the fixing step. Additionally, low fusing characteristics are required, hence the polyester resin should melt or flow as low in temperature as possible above the glass transition temperature, such as from about 1.degree. C. to about 40.degree. C. and preferably from about 15.degree. C. to about 35.degree. C., as measured by a capillary rheometer as for instance the Shimadzu CFT-500 Flowtester available from Shimadzu Corporation, which measures the resin's softening point temperature (T.sub.s), beginning of flow temperature (T.sub.1), and flow temperature (T.sub.2) at the manufacturer's standard condition by loading about 1.5 to about 1.8 grams of a pressed resin pellet sample in barrel with a chamber of 4 centimeters in length and 1 centimeter in diameter containing a die at the bottom of the barrel chamber with an orifice opening of 1 millimeter in diameter and 1 millimeter in length, and heating the barrel chamber with a piston loading of 20 Kg/cm.sup.2 from an initial temperature of 20.degree. C. to 130.degree. C. at a rate of 10.degree. C. per minute. It is generally observed that polyester resins utilized as low melting toner composition, such as illustrated herein, display a beginning of flow temperature (T.sub.1) of from about 80.degree. to about 92.degree. C. Additionally, polyester resins are desired that display broad fusing latitudes of from about 60.degree. C. to about 100.degree. C. This imposes an additional design criteria which avoids or minimizes a drastic drop in melt viscosity or melting too sharply, and which property can also be measured by the Shimadzu flowtester as the flow temperature T.sub.2. It is generally regarded that the T.sub.2 flow temperature correlates with fusing latitude, and hence in order for the aforementioned low fusing toners to display broad fusing latitude of from about 60.degree. C. to about 100.degree. C., it is necessary in embodiments that the T.sub.2 flow temperature should be of from about 15.degree. C. to about 50.degree. C. and preferably be from about 15.degree. C. to about 30.degree. C. higher than the beginning of flow temperature T.sub.1. For the prior art linear polyester resins utilized as toner compositions such as those mentioned in U.S. Pat. Nos. 3,590,000; 4,533,614 and illustrated herein Table 3, it is generally observed that these resins display low fusing characteristics of from about 132.degree. C. to about 142.degree. C., and narrow fusing latitude of from about 20.degree. C. to about 35.degree. C., as correlated with the Shimadzu Flowtester which indicates a beginning of flow temperature (T.sub.1) of from about 80.degree. C. to about 92.degree. C., and flow temperature (T.sub.2) is of from about 5.degree. C. to about 12.degree. C., and thus require high levels of oil to prevent offset to the fuser rollers. With the side chain polyesters of this invention, it is generally observed in embodiments that the beginning of flow temperature (T.sub.1) is from about 80.degree. C. to about 92.degree. C., and the flow temperature (T.sub.2) is from about 15.degree. C. to about 30.degree. C. higher than T.sub.1, and hence display low fusing characteristics, such as from about 135.degree. C. to about 142.degree. C., and accompanied by a broad fusing latitude of from about 50.degree. C. to about 60.degree. C. and higher, which avoids or minimizes the use of fuser or release oils as illustrated in some of the Examples that follow, reference Example XXXII, and in Table 4 herein.
From a research consideration of polyester monomer costs in the 1992 edition of Chemical Marketing Reporter (copyright by Schnell Publishing Company), and from research of the glass transition temperature of polyesters in the Polymer Handbook, 3rd (by Wiley Interscience), it appears that the least expensive monomers that can be utilized to obtain amorphous polyester resin is poly(diethyleneglycol-terephthalate) with an equilibrium glass transition of 20.degree. C. It is also observed that the poly(1,2-propanediol-terephthalate) resins can be obtained from the next least expensive monomers and display a glass transition of about 85.degree. C. Hence, in a preferred embodiment of the present invention, low cost polyester or oligomers can be obtained from inexpensive monomers, such as 1,2-propanediol, diethylene glycol and terephthalic acid or dimethyl terephthalate, by varying the glycol ratios such that glass transition temperatures of from about 40.degree. C. to about 70.degree. C. can be obtained with number average molecular weight of from about 1,500 to about 20,000 grams per mole useful for toner resin applications. The aforementioned low cost poly(1,2-propylene-diethylene-terephthalate) can also be capped with inexpensive unsaturated monomers, such as maleic anhydride, to provide economical endene polyesters, and further be polymerized with free radical initiators to yield low cost side chain polyesters. To demonstrate the applicability of this low cost polyester system utilizing 1,2-propanediol, diethylene glycol and dimethyl terephthalate, a series of polyester comprised of differing ratios of 1,2-propanediol and diethylene glycol and dimethylterephthalate were prepared as illustrated in Examples I to XVI, and the thermal properties thereof are provided in Table 1. A correlation of glycol ratio and number average molecular weight with the glass transition (Tg) and Shimadzu flow properties (T.sub.s, T.sub.1, T.sub.2) was then obtained, and using a statistical RS/1R software program available from BBN Software Products, the following empirical equations were generated: EQU D=62.2-0.159Tg-1.7T.sub.s -6.17T.sub.1 +6.255T.sub.2 Equation ( 1) EQU M.sub.n =1,333T.sub.2 31 525.2Tg-39,300-796T.sub.1 +98.7T.sub.sEquation ( 3) EQU P=100-D
wherein
D is the diethylene glycol ratio; PA1 P is the 1,2-propylene glycol ratio; PA1 Mn is the number average molecular weight of the polyester; PA1 Tg is the glass transition temperature of the side chain polyester; PA1 T.sub.s is the softening point of the polyester; PA1 T.sub.1 is the beginning of flow temperature of the polyester; and PA1 T.sub.2 is the flow temperature of the polyester. PA1 an, bn and cn are constants, and n is a number of from 1 to about 9, PA1 M.sub.n is the number average molecular weight of the polyester, PA1 M.sub.w is the weight average molecular weight of the polyester, PA1 D is the diethylene glycol ratio. PA1 P is the 1,2-propylene glycol ratio, PA1 Tg is the glass transition temperature of the polyester, PA1 T.sub.s is the softening point of the polyester, PA1 T.sub.1 is the beginning of flow temperature of the polyester, and PA1 T.sub.2 is the flow temperature of the polyester.
Using the above empirical correlation, the glycol ratio of 1,2-propylene to diethylene of the corresponding poly(1,2-propylene-diethylene-terephthalate) resin can be adjusted with its number average molecular weight to match any amorphous linear polyester of specified Tg, and Shimadzu flow properties T.sub.s, T.sub.1 and T.sub.2.
In in U.S. Pat. Nos. 3,590,000 and 4,525,445, there is disclosed a linear polyester comprised preferably of propoxylated bisphenol A and fumaric acid, and available as SPAR II.TM. from a number of sources, such as Atlas Chemical Company. This polyester resin can be utilized in toner compositions containing a black oxide pigment and can be utilized in the Xerox Corporation 3100 machine equipped with a noncontact fuser, which avoids hot-offset properties, and this is inferior to contact fusing applications as illustrated herein. This linear polyester material displays a glass transition temperature of 54.degree. C. as measured by the DSC, a softening point of 76.degree. C., a beginning of flow temperature of 82.degree. C. and flow temperature (T.sub.2) of 98.5.degree. C. as measured by the Shimadzu Flowtester. By substituting these aforementioned values into the above empirical equations 1 and 2, it can be calculated that a linear polyester comprised of poly(1,2-propylene-diethylene-terephthalate) with a glycol ratio of 34.6 to 65.4 of diethylene and propylene glycol, respectively, and of number average molecular weight of 5,852 should display similar thermal properties as the commercially available SPAR II, see Comparative Example XVIII, wherein an economical polyester comprised of (1,2-propylene-diethylene-terephthalate) with a glycol ratio of 34.6 to 65.4 diethylene and propylene glycol, respectively, and of number average molecular weight of 5,700, and which displays a glass transition temperature of 54.degree. C. as measured by the DSC, a softening point of 76.degree. C., a beginning of flow temperature of 82.degree. C. and flow temperature (T.sub.2) of 99.degree. C. as measured by the Shimadzu Flowtester. Also note Table 3, wherein the fusing results indicate similar low fusing temperature of about 132.degree. C. and hot-offset of 180.degree. C. for toners comprised of 98 percent by weight of linear polyester and 2 percent by weight of PV FAST BLUE.TM. pigment. Hence, a linear economical polyester comprised of poly(1,2-propylene-diethylene-terephthalate), estimated from Chemical Marketing Reporter to be of about 30 percent of the cost of SPAR II.TM., displays similar fusing performances of SPAR II. In yet another specific example, there is also disclosed in Japanese Patent Laid Open 44836 (1975), 37353 (1982), 109875 (1982) and 3031858-A (1991) and references therein, a linear polyester resin comprised of polybasic carboxylic acid, such as derived from ethoxylated bisphenol A, cyclohexanedimethanol and terephthalic acid. This aforementioned linear polyester material displays a glass transition temperature of 62.degree. C. as measured by the DSC, a softening point of 83.degree. C., a beginning of flow temperature of 91.degree. C. and flow temperature (T.sub.2) of 104.degree. C. as measured by the Shimadzu Flowtester. By substituting these aforementioned values into the above empirical equations 1 and 2, it can be calculated that a linear polyester comprised of poly(1,2-propylene-diethylene-terephthalate) with a glycol ratio of 16.6 to 83.4 of diethylene and propylene glycol, respectively, and of number average molecular weight of 2,600 should display similar thermal properties as the commercially available SPAR II.TM., see Comparative Example XVII, wherein an economical polyester comprised of (1,2-propylene-diethylene-terephthalate) with a glycol ratio of 16.6 to 83.4 diethylene and propylene glycol respectively, and of number average molecular weight of 3,100 and which displays a glass transition temperature of 62.degree. C. as measured by the DSC, a softening point of 83.degree. C., a beginning of flow temperature of 91.degree. C. and flow temperature (T.sub.2) of 104.degree. C. as measured by the Shimadzu Flowtester. Also see Table 3, wherein the fusing results indicate similar low fusing temperature of about 141.degree. C. and hot-offset of 200.degree. C. of toners comprised of 98 percent by weight of linear polyester and 2 percent by weight of PV FAST BLUE.TM. pigment. Hence, a linear polyester comprised of poly( 1,2-propylene-diethylene-terephthalate) is estimated from Chemical Marketing Reporter to be of about 25 percent of the cost of SPAR II.TM.. There is also disclosed in U.S. Pat. Nos. 4,533,614 and 4,957,774 a linear polyester resin comprised of dodecylsuccinic anhydride, terephthalic acid, alkyloxylated bisphenol A and trimellitic anhydride as chain extenders. Toner composites thereof display a glass transition temperature of about 56.degree. C. as measured by the DSC, a softening point of 78.degree. C., a beginning of flow temperature of 84.degree. C. and flow temperature (T.sub.2) of 98.degree. C. as measured by the Shimadzu Flowtester. By substituting these aforementioned values into the above empirical equations 1 and 2, it can be calculated that a linear polyester comprised of poly(1,2 -propylene-diethylene-terephthalate) with a glycol ratio of 18.8 to 81.2 of diethylene and propylene glycol, respectively, and of number average molecular weight of 2,540 should display similar thermal properties as the above polyester resin, see Comparative Example XIX, wherein an economical polyester comprised of (1,2-propylene-diethylene-terephthalate) with a glycol ratio of 18.8 to 81.2 diethylene and propylene glycol, respectively, and of number average molecular weight of 2,610 and which displays a glass transition temperature of 56.degree. C. as measured by the DSC, a softening point of 76.degree. C., a beginning of flow temperature of 84.degree. C. and flow temperature (T.sub.2) of 98.degree. C. as measured by the Shimadzu Flowtester. Also see Table 3, wherein the fusing results of the corresponding toners indicate similar low fusing temperature of about 143.degree. C. and 144.degree. C., and hot-offset of 200.degree. C. Hence, a linear economical polyester comprised of poly( 1,2-propylene-diethylene-terephthalate) is estimated from Chemical Marketing Reporter to be of about 20 percent of the cost of the above linear polyester.
There is disclosed in U.S. Pat. Nos. 4,940,644, 5,047,305, 4,049,447, and Canadian Patent 1,032,804, a linear polyester comprised of an amorphous aromatic polyester derived from an arylene radical and diol, and encompasses resins such as poly(neopentyl-terephthalate) comprised of terephthalate radical and neopentyl glycol, see Comparative Example XX, and Table 3 wherein substantially similar results are obtained utilizing the linear polyester comprised of (1,2-propylene-diethylene-terephthalate) with a glycol ratio of 24 to 76 of diethylene glycol and 1,2-propylene glycol, respectively. Also, the linear economical polyester comprised of poly(1,2-propylene-diethylene-terephthalate) estimated from Chemical Marketing Reporter to be of about 80 percent of the cost of the poly(neopentyl-terephthalate) resin. Moreover, in another specific example, utilizing the aforementioned empirical equations, the broadest fusing latitude possible for a linear polyester resin of low fusing temperature of from about 120.degree. C. to about 144.degree. C. can be estimated by the graphical overlap of calculated T.sub.2 values by varying both the glass transition temperatures of from about 50.degree. C. to about 65.degree. C., and with softening points of less than 80.degree. C. and beginning of flow temperature (T.sub.1) of less than 92.degree. C. In such calculations, it is found that the T.sub.2 values of no more than from about 10.degree. C. to about 15.degree. C. higher than T.sub.1 can be obtained. Hence, fusing latitudes of from about 50.degree. C. to about 100.degree. C. cannot be attained in toner compositions utilizing these linear amorphous polyesters. With side chain polyesters of this invention, an unsaturated moiety such as maleic anhydride of from about 0.01 to about 0.1 mole equivalents is utilized in preparing an endene polyester comprised of poly(1,2-propylene-diethylene-terephthalate-maleate), followed by its free radical polymerization to yield a side chain polyester as illustrated in Examples XXI to XXVI. The thermal properties of the side chain polyesters are listed in Table 4, and note that the beginning of flow temperature T.sub.1 is from about 80.degree. C. to about 92.degree. C. and the flow temperature T.sub.2 is approximately 15.degree. to about 30.degree. C., and the fusing latitude is from about 50 to about 60, considerably higher than the above linear polyester. Therefore, the economical side chain polyesters are advantageous in obtaining low fusing toners of from about 130.degree. C. to about 142.degree. C. and accompanied by broad fusing latitude, such as from about 50.degree. to about over 70.degree. C.
Also, there is disclosed in U.S. Pat. No. 4,525,445 a developer composition comprised of a linear polyester derived from fumaric acid, isophthalic acid and propoxylated bisphenol. Further, other toner compositions are known to contain linear polyester resins, such as those disclosed in U.S. Pat. No. 4,968,575, a linear polyester blocked with rosin compound, and U.S. Pat. No. 5,004,664, a linear polyester prepared from the ring opening polymerization of cyclic monomers, and U.S. Pat. No. 5,057,392, a blend of resins comprised of a crystalline and amorphous polyesters; U.S. Pat. Nos. 4,543,313 and 4,891,293 wherein there are disclosed linear thermotropic liquid crystalline polyester resins, the disclosure of which is totally incorporated herein by reference. Other U.S. Patents of interest disclosing linear polyesters are U.S. Pat. Nos. 4,052,325; 3,998,747; 3,909,482; 4,288,516; 4,140,644; 4,489,150; 4,478,423; 4,451,837; 4,446,302; 4,416,965; 4,866,158; 5,153,301; 5,116,713; 5,043,242; 5,045,424; 5,049,646; 5,102,762; 5,110,977 and 4,837,394.
Attempts have been made to overcome the disadvantages of narrow fusing latitude of polyesters such as from about 10.degree. to about 40.degree. C. For instance, developer compositions containing modified polyester resins with a polybasic carboxylic acid are disclosed in Japanese Laid Open Nos. 4836 (1975); 3753 (1982) and 109875 (1982); and also in U.S. Pat. No. 3,681,106; and more specifically branched or crosslinked polyesters derived from polyvalent acids or alcohols are illustrated in U.S. Pat. Nos. 4,298,672; 4,863,825; 4,863,824; 4,845,006; 4,814,249; 4,693,952; 4,657,837; 5,143,809; 5,057,596; 4,988,794; 4,981,939; 4,980,448; 4,960,664; 4,933,252; 4,931,370; 4,917,983 and 4,973,539. The resulting modified polyester resins by branching or crosslinking improve the hot-offset resistance only at a sacrifice of the low fixing temperature performance. Other disadvantages with branched or crosslinked polyesters are high content of gel and inferior unacceptable dispersibility properties with colored pigment for color toner composition, in reduced gloss properties, such as from about 5 to about 40 gloss units as measured by the Gardner Gloss metering unit as reduced transparency efficiency, such as from about 5 to about 60 percent efficiency as measured by the Match Scan II spectrophotometer available from Diano. Moreover, extrusion low melting crosslinked polyesters that can be selected as toner resins and are prepared, for example, from SPAR.TM. type polyesters are illustrated in copending patent applications U.S. Ser. No. 814,641 and U.S. Pat. No. 5,227,460, the disclosures of which are totally incorporated herein by reference. The aforementioned resins in embodiments have about a 30 percent gel content, and possess a broader fusing latitude than known SPAR.TM. polyester resins. In the present invention, the second step of reactive extrusion is minimized or avoided. Additionally, the polyesters of this invention differ in that the polyester is a side chain whereas the resin of the U.S. Ser. No. 814,641 is crosslinked resulting from the polymerization of unsaturated moieties through the polyester chain and wherein a high gel content is obtained. The side chain polyester of this invention in embodiments contains no gel, and can be easily dispersed with carbon black or colored pigment and result in high projection efficiency and high gloss. Additionally, the materials cost and process cost of the side chain polyesters of this invention is considerably lower, for example about from about 25 percent to about 50 percent less than the cost of crosslinked SPAR II.TM. resin.
The following patents are also mentioned: U.S. Pat. Nos. 5,156,937; 4,981,923; 4,990,424; 5,037,715 and 5,147,747, wherein toner compositions are comprised of blends of different polyesters, one of which is characterized with low molecular weight and the other as high molecular weight; and 4,877,704 which discloses a polyester resin of nonlinear copolymer having an aliphatic hydrocarbon group containing 3 to 22 carbon atoms, said copolymer being obtained from polymerization of an etherified bisphenol A monomer, a dicarboxylic acid monomer, and a polyhydric alcohol.